DE10002230A1 - Adaptive robot guidance method, uses successive measurements with master piece and actual component for determining offset vectors used for adaption of robot movement program - Google Patents

Abstract

The robot guidance method uses an optical measuring system with at least one laser illumination device (7) and a video camera (6) for obtaining component measurements via a triangulation method, for providing control signals for correcting the robot movements. An initial measuring step uses a master piece (9) with the same geometry as an actual component (5), held by the industrial robot in the component position, for measurement by the measuring system, with subsequent measurement of the actual component, for determining offset vectors, used for adaption of the movement program. An Independent claim for a robot guidance device is also included.

Description

The invention relates to a method and an apparatus for automated Management and control of the movements of an industrial robot on the basis of externally arranged optical measuring systems that act as calibrated devices with the help of laser lighting devices and camera technology on the basis the triangulation technique the geometric features of the treatment Missing components and control signals for the correction of Derives robot movements.

The requirement to adapt the robot movements to the respective ones current geometric conditions of the components to be treated is in increasing the basic requirement for the successful use of Industrial robotics, especially when machining tolerant components is permitted.

A large number of solutions were used to implement this adaptivity developed that tries with different technical basis, the real Geometry relationships in the machining area to be recorded and in Implement correction signals. So there are solutions where that technological tool, for example an arc welding torch, with tactile sensors, which point the location of surfaces scan. In part, the technological tool itself is used as a tactile sensor used when, for example, the welding wire or the gas cap of the Welding torch will be able to take advantage of electrical contacts via auxiliary circuits to touch the components capture (DE-OS 28 47 169). Furthermore, solutions are available in which the Surface scanning implemented with non-contact distance sensors is (DE-OS 27 41 728), the distance-dependent signaling Obtaining correction signals can be used.

The disadvantage of these solutions is that they are comparatively large mechanical ones Assemblies must also be attached to the technological tools,  which negatively affects the accessibility of the tool due to its space requirement influence. Another disadvantage is that the reliability of these additional Measuring systems because of the close proximity to the process (e.g. negative influence from a welding process in the form of heat, magnetic fields and strong Pollution) and the required fault-prone cabling is limited. Ultimately, it is also a disadvantage that the measurements on the Component surfaces are made exclusively in punctiform form, with the measuring point size depends on the physical measuring principle and can only be influenced to a limited extent can. While the tactile facilities are based on existing ones Tool components (e.g. gas cap of the welding torch) not the above Disadvantages mentioned with regard to space requirements occur in these systems the problems of auxiliary times in connection with slow robotic Search movements in the foreground. Common disadvantage of all of these Systems are the limitation of the measuring point to one measuring point.

Optical measuring systems based on line-shaped or planar receiver structures offer the possibility of avoiding these disadvantages of point-shaped scanning. Various applications of photo receivers (CCD cameras) with suitable lighting devices are known in order to record the contours from the surface using the light section method, to analyze them and to derive control signals / correction signals for robot movements therefrom. For example, patent EP 0 275 322 describes a method for determining the position data during arc welding, the image evaluation at the welding point being carried out using the light section method. In the patent DE-OS 31 44 843 a method for operating a manipulator working as a welding robot is presented. Here, a light pattern is projected onto the workpiece surface, which is recorded by a camera while the programmed path is being followed. The distortions of the light pattern are used to correct the path. In the DVS reports, volume 118 ( 1989 ), pp. 139-142, a solution of an optical seam guidance system is described in which 2 lasers project lines onto the components which are recorded by a CCD matrix camera. According to the different tasks for which this sensor is to be used, different design versions, e.g. B. also refer to systems with an internal axis of rotation. To avoid the disadvantages that exist with these additional components on the welding torch, it is proposed in EP 0 118 075 to arrange the camera and possibly also the lighting devices in the welding torch itself, with the image being taken through the gas cap. However, the reliability of such a complex arrangement is questionable. A comparable solution is also described in US 4,673,795 for laser processing. Here, the transmission of image information is realized via the laser optics or via the glass fiber cable simultaneously with the laser light energy, which can be evaluated for positioning tasks or for process controls. However, this solution cannot be applied to general applications of a robot control regardless of laser technology.

A complete system for measuring component geometries as a compact one Device in connection with an arc welding head is also used in the Patent US 5 715 375 presented. As with the ones described above Solutions in this patent is aimed at a goal with which possible compact arrangement on the welding head directly the component scenes in immediate Close to the welding process. As a major advantage become both a certain independence from the component geometry as well robot tolerances expected.

Common to all solutions is the disadvantage that they are comparatively large mechanical assemblies in addition to the technological tools are fasten, the accessibility of the tool due to their space requirements influence negatively. Another disadvantage is that the reliability of this optical measuring systems because of the close proximity to the process (e.g. negative Influence from a welding process in the form of heat, extraneous light, magnetic fields and heavy pollution) and the required interference-prone cabling is limited. The use of these compact systems is also connected in each case with the disadvantage that the management of the technological tool to align the measuring system Component surface determined. This means that unfavorable reflection conditions are eliminated  technological point of view inevitable. These can be too imprecise or lead to unreliable modes of operation.

Another disadvantage is that the rigid arrangements within the measuring systems only certain measuring ranges and specified object sizes can be measured can.

The technical and patent literature lacks solutions to avoid the process-related loads and the other disadvantages mentioned optical systems at a comparatively large distance from the process position. Possible causes are the risk of instability System mounts, the effects of which at large measuring distances enlarge, and the insufficient feedback of movement tolerances of the Robot considered for this.

The comments on the prior art show that despite the variety of solutions for adaptive position control of robots including powerful image processing systems in connection with laser scanners for the users serious problems such as high reliability of the Overall system, especially no disruptive influence from the technological Manufacturing processes, minimization of auxiliary times and thus no Auxiliary movements of the robot and, last but not least, the avoidance of additional ones Attachments to the technological tool (welding torch or similar) for Ensuring free access to the tool in critical Component positions are not met.

The invention thus pursues the aim of a method and an apparatus for automated guidance and control of the movements of an industrial robot to create on the basis of externally arranged measuring systems, which of free selectable positions outside of the interference areas by the technological processes the geometric features of the treated Measure components with a large measuring distance and control signals for them Derive correction of robot movements, taking into account possible interference factors  regarding insufficient measuring system mounts or tolerances of the Robot movements are taken into account independently.

It is therefore an object of the invention to provide a method and an apparatus for automated control of the movements of an industrial robot on the basis to develop optical measuring systems using laser lighting facilities and camera technology based on the triangulation principle Geometric features of the components to be treated and measured Derive control signals for the correction of robot movements.

According to the invention this object is achieved in that the Measurement system from at least two spatially separated Units, one unit being a CCD camera and the second and each another unit represents a laser line lighting system. The CCD camera and the laser line lighting systems are made of rigid supports in one angular arrangement held to each other. Form together with the robot foot these rigid supports form a mechanical unit. Regarding their directions of action are the CCD camera and the laser systems to be measured Surface areas of the workpiece aligned. CCD camera and Laser line humidification systems form calibratable measuring systems with one fixed reference to the coordinate system of the robot. The consideration of thermal changes in the carrier and inadequacies of the Industrial robots is achieved in that at cyclical intervals Exploitation of tool changing systems by the robot well-known sample part with comparable geometry to the usual Manufacturing locations is positioned briefly to do a comparison measurement with the surveying system. As a result of the comparison measurement correction vectors are calculated which are used for the intended correction of the Position of the tool can be used as an offset for real components.

With the implementation of a method and a device according to the invention for automated guidance and control of the movements of a Industrial robots based on externally arranged optical measuring systems The following advantages result:  

It succeeds in influencing the components of the measuring system through the manufacturing process to set up in safe positions. These positions are freely selectable. They leave with regard to a reliable recognition of the characteristics optimize by choosing favorable angles of attack at any measuring distance. A Adaptation to different measuring ranges is possible without any problems. At the Robotic hands are not additional mechanical components accommodate. All of these measures significantly improve reliability of the overall system. In addition, the accessibility of the work tool not deteriorated by additional components. The externally arranged Systems can send the measurement to the robot before it is retracted Perform component, which leads to time savings or minimized auxiliary times. Through the possibility of self-diagnosis of the overall system in connection with a sample that is held by the robot at the measuring point accuracy-reducing effects such as wear and tear on the robot be compensated. The implementation of the solution according to the invention is realized thus an automatic production of high-tolerance components Reliability and accuracy. Ultimately, an additional for the user Cost advantage effective because of diverse tools to secure the Operation under immediate process conditions such as cooling devices and Protective glasses can be dispensed with.

The invention is described below using an example of a cutting robot explained in more detail with reference to the accompanying drawings, wherein

Fig. 1 shows a spatial arrangement of the essential components of the adaptive robot guidance on the basis of externally arranged optical measuring systems and

Fig. 2 show a possible representation of the position of the structures to be measured in the image of the camera.

An industrial robot 1 is operated in a hanging position with an attachment to a carrier 2 . The industrial robot 1 has a cutting torch 3 as a working tool. The cutting torch 3 is fastened to the wrist of the industrial robot 1 in a known manner using components of a tool changing system. In the working area of the industrial robot 1 , a workpiece holder 4 is positioned on which the component 5 is placed for processing. Above the processing area, an image recording unit 6 is arranged on the common support 2 and a laser line projector 7 is offset laterally from this. Both the image recording unit 6 and the laser line projector 7 are aligned with the component 5 with regard to their directions of action. In addition, a tool changing station 8 is rigidly attached to the carrier 2 in the processing space of the industrial robot 1 , on which the cutting torch 3 and a sample 9 can be placed if required.

The following function is achieved with this arrangement:

At the beginning of the machining process and at regular intervals, the industrial robot 1 removes the sample 9 from the tool changing station 8 and holds it in the vicinity of the usual position of the component 5 on the workpiece holder 4 . The laser line projector 7 illuminates the sample with the line pattern 10 , which is captured by the image recording unit 6 . In the connected evaluation system, the characteristics are determined from the line pattern in the image, for example line jump heights, slopes, break points of the lines, kinks, etc. From the knowledge of the relative arrangement of the laser line projector 7 and the image recording unit 6 with respect to one another, dimensions which are dimensioned from these features, for example surface inclination, position of an edge in space, thickness or absolute height of the component 5 or sample piece 9 are calculated and transformed into the coordinate system of the industrial robot 1 . These dimensioned position sizes of the sample 9 determined in this way are compared with program-internal reference values and form a spatial offset vector 1 for shifting the machining program of the industrial robot 1 . This offset vector 1 is buffered until the measurement of the sample 9 is repeated.

In the production phase, the sample 9 is placed in the tool changing station 8 , the industrial robot 1 carries the cutting torch 3 . Instead of the sample 9 , the component 5 then present is measured under the same conditions. The features are determined using the same algorithms and the positional deviations of the component 5 in comparison with the programmed reference values are determined as offset vector 2 . The difference between offset vector 2 and offset vector 1 is used to transform the movement program of the industrial robot 1 for the execution of the cutting process, for example the implementation of contour cuts on obliquely lying profiles, on the component 5 .

Advantages in the application described are the possibility of placing the image recording unit 6 and the laser line projector 7 at a large distance from the component 5 and thus from the processing point, so that they are not influenced by the cutting process. The position of the component 5 is already determined during the start-up of the industrial robot 1 . Possible thermal distortion of the entire system including carrier 2 and workpiece holder 4 as a result of the cutting processes are compensated for by the method described above with occasional reference measurements.

List of the reference symbols used

1

Industrial robots

2

carrier

3rd

Cutting torch

4

Workpiece holder

5

Component

6

Image acquisition unit

7

Laser line projector

8th

Tool changing station

9

Sample

10th

Line pattern

Claims (2)

1. A method for the automated guidance and control of the movements of an industrial robot on the basis of optical measuring systems which measure components with the aid of laser lighting devices and camera technology based on the triangulation technique and derive control signals for the correction of robot movements therefrom, characterized in that externally arranged, calibrated measurement systems are used, with which in a first method step a sample 9 with a geometry corresponding to the real component 5 , which is temporarily held by the industrial robot 1 at the position in which the real component 5 is usually positioned, absolutely in terms of its characteristics Coordinate system of the industrial robot 1 is measured, and with which the real components 5 are also measured in the further steps after an identical evaluation method, so that the comparison of the determined positions of the features with reference values first offset vectors are determined and that the difference between the offset vectors determined for the real components 5 and the offset vector of the sample 9 transforms the motion program of the industrial robot 1 for the execution of the technological movement. 2. Device for performing the method according to claim 1, characterized in that an image recording unit 6 and one or more laser line projectors 7 , which generate line patterns with one or more lines, are rigidly attached to a common support 2 , image recording unit 6 and Laser line projectors 7 are spatially separated from one another and are aligned with their directions of action on the processing point and the carrier 2 forms a rigid unit together with the base of the industrial robot 1 .